Apparatus for simultaneously imparting an alternate series of thread forms on a workpiece



G. L. WIEBER 3, APPARATUS FOR SIMULTANEOUSLY IMPARTING AN ALTERNATE SERIES OF THREAD FORMS ON A WORKPIECE Original Filed July 30. 1963 2 Sheets-Sheet l July 12, 1966 July 12, 1966 G. L. WIEBER 3,260,100

APPARATUS FOR SIMULTANEOUSLY IMPARTING AN ALTERNATE SERIES OF THREAD FORMS ON A WORKPIECE Original Filed July 30. 1963 2 Sheets-Sheet 2 INVENTOR.

/\ wwsgmm L..Wie r BY Z w ax United States Patent C) 14 Claims. (Cl. 72-469 The present application is a division of my copending application, Serial No. 298,766, filed July 30, 1963.

This invention relates in general to apparatus for simultaneously imparting an alternate series of thread forms on a workpiece and more particularly relates to apparatus for simultaneously imparting an alternate series of thread forms where one form extends radially outwardly a substantially greater amount than the next alternate form on a screw shank or the like.

The thread rolling of screw or bolt workpiece shanks is normally accomplished by thread rolling dies having parallel grooves therein, the grooves being substantially identical in configuration. In some thread rolling dies, the dies are reciprocated past each other with the path of motion of one of the dies being at a slight angle to the axis of the other die (which is usually stationary).

The instant apparatus relates to the use of a pair of die blocks which have reciprocatory relative motion in substantially parallel plane.

In order to provide the desired high-low thread forms alternating on the workpiece shank, it has been found necessary and desirable to provide adjacent grooves which have initially different depths in the die blocks, initially different widths, and the side walls converge at different rates along the length of the respective grooves. It has further been found necessary and desirable to provide a wide acceptance angle for the groove which provides the radially larger thread which starts the material of the workpiece shank moving from its original grain structure with a semigentle movement rather than an abrupt change which would occur with a sharper acceptance angle.

It is a general object of this invention to provide apparatus for thread rolling relatively high and relatively low threads on a screw shank in alternate arrangement.

It is a further object of this invention to provide apparatus for providing screw threads of the aforenoted type in.a manner which is fast, economically feasible, and provides a uniform high quality product. i

A still further object of this invention is to provide apparat-us of the aforenoted type wherein the tooling may be made by standard techniques and which has relatively long life in actual use.

The novel features which are characteristic of the invention are set forth with particularlity in the appended claims. The invention itself, however, booth as to its organization and its method of operation, together with additional objects and advantages thereof, will best be understood by the following description of a specific embodiment when read in conjunction with the accompanying drawings in which:

FIG. 1 is a semidiagrammatic view of fixed and reciprocating die blocks and their relative relationships during the thread rolling operation;

FIG. 2 is a side elevational view indicating the product obtainable by the disclosed apparatus;

FIG. 3 is a semi-diagrammatic side elevational view of the stationary die block shown in FIG. 1;

FIG. 4 is a semidiagrammatic side elevational view similar to FIG. 3 showing the die block which reciprocates in FIG. 1;

FIG. 5 is a semidia-gram-matic showing of a plurality of outline sectional views along the grooves in the die blocks showing the varying rates of changes in the depth and width of the grooves along the length thereof;

FIG. 5A is a sectional view along lines 5A-5A of FIG. 4, said view being considerably enlarged in scale.

FIG. 6A through 6B are a plurality of sectional views, greatly enlarged, taken along the respective lines 6A, 6B, 6C, 6D, and 6B of FIGS. 3 and 4 indicating the various changes represented along the sectional lines and illustrate the thread forming characteristics of the die related to the flow of material axially to the workpiece as it would pass through the areas designated by lines 6A-6A through 6E6E (which are normal to the thread form) of FIGS. 3 and 4; and

FIG. 7 is a sectional view along lines 77 of FIG. 5A.

Means for feeding screw blanks for cooperation with a pair of relatively reciprocating die members are well known and shall not be discussed further. This invention relates to the die blocks 10 comprising a stationary die block means 12 and a reciprocating die block means 14. As shown in FIG. 1, the die block 14 is operable to move substantially parallel to die block 12 to roll threads on a workpiece 16 to provide alternate high threads 18 and relatively low threads 20 simultaneously. It will be noted that the high threads 18 extend radially outwardly a considerably greater distance than do the alternate low threads 20. The screw blank 16 has a pointed tip 24 and a head portion 22 which is cross-slotted or otherwise formed for imparting rotation to the blank. The precise form of head 22 and entering end 24 may be varied within wide limits depending upon the application desired and form no part of the instant invention.

While the die blocks 12 and 14 are of different overall lengths, as is conventional, the essential characteristics of each die block are the same and unless specific differences are discussed between the different die blocks, it will be assumed that the identical feature will be found on both except for considerations of left and right hand faces in opposition to each other. The die block 12 and the die block 14'are each formed with alternate grooves which are generally parallel to each other and differ from each other. The grooves traverse the die block at a predetermined angle as determined by the lead and diameter of the finished screw desired. As shown in FIGS. 3 and 4 the grooves 26 and 30 in full line are shallower grooves relative to grooves 28 and 32 shown in dotted line. The shallower grooves impart the thread form 20 on the screw blank whereas the deeper grooves 28 and 32 impart a thread form 18 on the screw blank.

As can be perceived intuitively from FIGS. 5 and 5A, eachof the grooves 26, 30 and 28, 32 progressively vary in width and depth along the length thereof and at different rates relative to each other. As shown in FIG. 5, outline sectional views taken as indicated along FIGS. 3 and 4, indicate the progressive change along the length of the grooves. FIGS. 6A through 6E correspond to the outline sectional views and show the gathering of the material from the screw blank as the thread is being formed.

The stationary die block 12 has an entering end portion 34 and a trailing end portion 36 wherein the operating face of the die block is recessed slightly for respeotively facilitating entrance of the screw blank and removal of same from between the die blocks as is conventional. Each of the die blocks 12 and 14 have an ironing portion 38 where the grooves are of constant width and depth for a predetermined portion of the groove length for purposes of truing up the blank and the screw thread formed thereon after they have been formed by the die blocks. I

Turning now to FIGS. 5A and 7, the die blocks have an operating face 40 in which the grooves 30 and 32 are formed. (Grooves 26-28 are similar to grooves 30- 32 except for overall absolute length.) The groove 32 for forming the thread 1 8 has opposed side walls 42 and 44 and a bottom wall 46 which changes in character at 48 as shallbe described. As can be been in FIG. 5A, the side walls 42 and 44 progressively converge toward each other and the bottom wall 46 progressively comes closer to the operating face 40, i.e., the groove becomes progressively shallower for a major portion of its length. This is perhaps best illustrated in FIG. 7. The groove 32 may be formed by first passing a cutter having an outline shape as shown at 6B in FIG. 5 across the die face parallel to surface 40 and then passing a cutter having an outline shape such as shown in FIG. 6A across the face 40 while progressively relatively moving the cutter and die block on an angle to each other so that the groove becomes shallower. After the second cutter has run out with the first cutter (for example a 30 cutter) the second cutter (for example a 60 cutter) having an outlined form as shown at 6A is superimposed upon the first groove, said second cutter being moved at an inclination angle relative to the die block so that the depth of the groove blends into the form 6E. The narrower angle cutter forms the bottom surface 48 of the groove and the intersection where the two cutters remove the stock and blend together on the different angles is shown at 50 in FIG. 7, the slope of the side walls 42 and 52 are different, caused by the different angularities of the two different cutters. The groove 30 is formed by a single cutter (for example a 60 cutter) to provide side Walls 5-4 and 56 which are converging toward each other and a bottom wall 58 which is moving toward surface 40 at a constant rate along the length thereof except for ironing portion 38. a

As shown in FIGS. 6A through 6E, a blank interposed between the two die blocks 12 and 14 will form the threads 18 and 20. FIG. 6A is a sectional view showing the gathering of the material approximately at the start of the thread forming operation. The wide acceptance angle of groove 32 at the start of the groove is efficacious to displace and gather the material from the screw blank :16. FIG. 6B is a projection at approximately 30% of the thread transformation, it being noted that thread portion 20b is quite well filled out whereas thread portion 18b is not. The projection in FIG. 60 shows the thread 20c is almost completely filled out whereas 180 is not formed, the projection being taken at approximately 60% of the thread transformation. The projection shown in FIG. 6D shows that the thread 20 is now fully formed whereas thread portion 18d is only about 90% formed and FIG. 6E shows the complete thread formation of both threads 18 and 20 at the finished portion of the die. FIGS. 6A through 6B are actual projections respectively of one-half, three, five and seven turns of a screw blank on a thirty times size scale. However, it will be realized that in rolling screws, the percentage of thread forming transformation per turn of the blank will vary depending upon size of blanks, etc.

The ironing section 38 on the die block allows the screw blank to regain a circular shape from an oval shape and trues up the threads. The threads that are formed by this method are found to be quite strong and well formed.

It will be noted as shown in FIG. 6A that the groove 62 has a wide mouth which provides a wide acceptance angle which starts the material moving on the screw iblank from its original grain structure toward forming the very high thread with a semigentle movement rather than an abrupt change that would occur with a much narrower mouth. -It will be further noted that the grooves 30 and 32 are of different depths along the length thereof, are of different widths along the length thereof and that the grooves converge at different rates. Also it will be noted that the low thread 20 is fully formed prior to the formation of the higher thread 18.

Although a specific embodiment of the apparatus for simultaneously forming high and low threads on screw blanks have been shown and described, it is with full awareness that many modifications thereof are possible. The invention therefore, is not to be restricted except insofar as is necessitated by the prior art and by the spirit of the appended claims.

I claim:

1. A thread rolling die comprising a die body having a thread rolling surface, said surface being characterized as having a plurality of thread form-ing grooves therein, a first groove of said plurality of grooves being characterized as being disposed in a predetermined plane and having a predetermined length, said first groove having a predetermined depth in a first portion thereof and a predetermined width at said first portion, said first groove having a second predetermined different depth and second predetermined width in a second portion spaced from said first portion along the length thereof, a second groove in said surface disposed in the plane parallel with said first predetermined plane and immediately adjacent said first groove, said second groove having a width and a depth in the first portion thereof immediately adjacent to said first portion of said first groove which differs from the width and depth of said first groove, said second groove in a second portion thereof adjacent to the second portion of said first groove having a width and depth which differs from the width and depth of said second portion of said first groove whereby threads of different size may be simultaneously rolled on a workpiece by said first and second grooves.

2. The die set forth in claim 1 wherein grooves identical to said first and second grooves are alternately disposed in spaced array on said thread rolling surface of said die, each groove being disposed substantially parallel to the other grooves in any plane normal to the axes of said grooves all of said first grooves having substantially identical depths and widths and all of said second grooves having substantially identical depths and widths.

3. The die set forth in claim 2 wherein the width and depth of said first and second grooves progressively change along the major extent of each groove.

4. The die set forth in claim 3 wherein the rate of change of the width and depth of said first and second grooves along the length thereof is different.

5. The die set forth in claim 4 wherein said first groove is substantially wider and substantially deeper than said second groove at said first portion thereof and is substantially deeper but only as wide at said second portion thereof.

6. The die set forth in claim 5 wherein the first portion of said first and second grooves is adjacent the starting edge of the thread forming surface of the die and said second portion is adjacent the finish end of said thread rolling die, said first groove converging in width and lessening in depth at a faster rate than the converging in width and lessening of depth of said second groove.

7. The die set forth in claim 6 wherein each of said first and second grooves are respectively of constant width and depth for a predetermined portion along the lengths thereof adjacent the finish end of said thread rolling die to provide an ironing section on said die.

8. A pair of generally rectilinear thread rolling dies adapted for relative rectilinear parallel movement with a workpiece blank therebetween to provide alternate high and low thread forms on the workpiece blank, each of said dies being characterized as having a thread forming face adapted to be disposed in opposition to said thread forming face of the other die, one of said die members being characterized as having a first surface on the thread forming surface thereof which is substantially coplanar throughout the entire extent thereof, first and second alternate groove means disposed in said first surface in parallel array, said first groove means adjacent the starting edge of said thread forming surface having a predetermined depth and predetermined width, said second groove means adjacent said starting edge of said thread forming surface having a second and substantially lesser predetermined depth and width, said first and second groove means at a position along the length thereof spaced from said starting edge having second and different predetermined widths and depths relative to the width and depth at said first position and relative to each other.

9. The pair of dies set forth in claim 8 wherein groove means identical to said first and second groove means are alternately disposed in spaced array on said thread rolling surface of said pair of dies, each groove means being disposed substantially parallel to the other groove means being disposed substantially parallel to the other groove means, in any plane normal to the axes of said groove means all of said groove means having substantially identical depths and widths.

10. The pair of dies set forth in claim 9 wherein the width and depth of said first and second groove means progressively change along the major extent of each groove means.

11. The pair of dies set forth in claim 10 wherein the rate of change of the width and depth of said first and second groove means along the length thereof is different.

12. The pair of dies set forth in claim 11 wherein said first groove means is substantially Wider and substantially deeper than said second grooved means at said first portion thereof and .is substantially deeper but only as wide as said second portion thereof.

13. The pair of dies set forth in claim 12 wherein the first portion of said first and second groove means is adjacent the starting edge of the thread forming surface of the die and said second portion is adjacent the finish end of said thread forming surface of the die, said first groove means converging in width and lessening in depth at a faster rate than the converging in width and lessening in depth of said second groove means.

14. The pair of dies set forth in claim 13 wherein each of said first and second groove means are respectively of constant width and depth for a predetermined portion along the length thereof adjacent the finish end of said thread forming surface of the die to provide an ironing section on said thread forming surface of the die.

References Cited by the Examiner UNITED STATES PATENTS 370,354 9/1887 Rogers 809 440,333 11/1890 Rogers 80-9 461,620 10/1891 Rogers 80--9 2,183,688 12/1939 Olson 80-9 2,183,689 12/1939 Olson 80--9 CHARLES W. LANHAM, Primary Examiner.

E. D. OCONNOR, Assistant Examiner. 

1. A THREAD ROLLING DIE COMPRISING A DIE BODY HAVING A THREAD ROLLING SURFACE, SAID SURFACE BEING CHARACTERIZED AS HAVING A PLURALITY OF THREAD FORMING GROOVES THEREIN, A FIRST GROOVE OF SAID PLURALITY OF GROOVES BEING CHARACTERRIZED AS BEING DISPOSED IN A PREDETERMINED PLANE AND HAVING A PREDETERMINED LENGTH, SAID FIRST GROOVE HAVING A PREDETERMINED DEPTH IN A FIRST PORTION THEREOF AN A PREDETERMINED WIDTH AT SAID FIRST PORTION, SAID FIRST GROOVE HAVING A SECOND PREDETERMINED DIFFER DEPTH AND SECOND PREDETERMINED WIDTH IN A SECOND PORTION SPACED FROM SAID FIRST PORTION ALONG THE LENGTH THEREOF, A SECOND GROOVE IN SAID SURFACE DISPOSED IN THE PLANE PARALLEL WITH SAID FIRST PREDETERMINED PLANE AND IMMEDIATELY ADJACENT SAID FIRST GROOVE, SAID SECOND GROOVE HAVING A WIDTH AND A DEPTH IN THE FIRST PORTION THEREOF IMMEDIATELY ADJACENT TO SAID FIRST PORTION OF SAID FIRST GROOVE WHICH DIFFERS FROM THE WIDTH AND DEPTH OF SAID FIRST GROOVE, SAID SECOND GROOVE IN A SECOND PORTION THEREOF ADJACENT TO THE SECOND PORTION OF SAID FIRST GROOVE HAVING A WIDTH AND DEPTH WHICH DIFFERS FROM THE WIDTH AND DEPTH OF SAID SECOND PORTION OF SAID FIRST GROOVE WHEREBY THREADS OF DIFFERENT SIZE MAY BE SIMULTANEOUSLY ROLLED ON A WORKPIECE BY SAID FIRST AND SECOND GROOVES. 